Endangered Status The California Least Tern, a subspecies of the Least Tern, is on the U.S. Endangered Species List. It is classified as endangered in California. This subspecies of Least Tern was declared endangered in 1970, but the interior and east coast populations have since also achieved that distinction. The destruction of its habitat by human activities and development has put the species in peril. Where it still finds nesting habitat, it is also vulnerable to predators and to human disturbance when bathers and beach strollers enter its nesting colonies. Least Terns will sometimes abandon their nests if they have been disturbed. Because of this tern's habit of nesting on low sandbars, whole colonies are sometimes destroyed by very high tides.